Eksplorasi Protein dari Sponge Asal Perairan Pulau Nias dan Binuangeun yang Mengkatalisis Polimerisasi Silika

Abstract

Silica, polymerized silicon dioxide, was widely used as raw materials for industries, such as food industry, semiconductor, electronic and medical equipment. Marine sponges (Phylum porifera) were living system that can produce a remarkable diversity of nanostructured silicates at ambient temperature and near-neutral pH. In contrast to living system, synthesis of these materials in industry require extreme of temperature, pressure, and pH with addition surfactant that can cause environmental pollution. Isolating protein that can catalyze nanostructured silica polymerization will make a new route for silica development under mild conditions using protein/enzyme biocatalyst. This research was aimed to extract and analyze protein from Nias Island Sea sponges and Binuangeun Sea sponges and to study their activity to polymerize tetraethoxyorthosilicate (TEOS). Protein in silica spicule of sponge was isolated by collecting silica spicule and soaked in HF/NH4F buffer (pH 5,0) for dissolving silica and releasing this protein. Then, protein was dialyzed and centrifuged. Activity of this protein to polymerize substrate tetraethoxyorthosilicate was measured by colorimetric molybdate assay. Protein of Sponge ST1 (from Binuangeun Sea) and protein of Sponge ST3 (from Nias Island Sea) have the same moleculer weight about 21.4 kDa and the same shape (filament) and size. Both of them have the length approximately 0,1 mm and diameter 10 mm. Protein of Sponge ST1 (250 ml, protein concentration less than 5 mg/ml) could polymerize 15,9 μmol TEOS after 12 hours reaction at room temperature and near-neutral pH and protein of Sponge ST3 could polymerize 3,0 μmol TEOS in the same reaction conditions. Silica formed from polymerization reaction by protein Sponge ST1 during 48 hours, coated this protein and increased its diameter four times. Sponge ST5, ST6 and ST7 which have unique microscleres silica spicule were potential to become sources of protein that can catalyze unique shape of biosilica. Sponges which have no silica spicule such as Sponge St8 and ST9 were not potential to become protein sources.

Silika merupakan polimer dari silikon dioksida yang banyak digunakan sebagai bahan dasar untuk pembuatan peralatan, antara lain filter agent, cutter, polisher yang digunakan pada industri pangan; bahan pelapis alat-alat semikonduktor dan elektronik; biochips, biosensor, kit analisis, stateskop dan peralatan medis lainnya. Sponge (Filum porifera) merupakan organisme yang secara alamiah dapat membentuk struktur silika yang padat dan sangat teratur pada suhu kamar dan pH netral. Pembentukan silika ini terjadi dengan bantuan protein silicatein. Di industri, proses pembentukan silika memerlukan kondisi suhu dan tekanan tinggi, pH ekstrim dan penambahan bahan kimia yang dapat mencemari lingkungan. Isolasi protein yang terlibat dalam pembentukan silika pada sponge membuka peluang penggunaan katalis protein untuk membuat silika secara invitro pada suhu yang relatif rendah dan pH netral. Penelitian ini bertujuan untuk melakukan isolasi protein yang mengkatalisis polimerisasi silika dari beberapa spesies sponge asal perairan Pulau Nias dan Binuangeun serta menganalisis aktivitasnya terhadap substrat tetraethoxyorthosilicate (TEOS).